This invention relates generally to electronic devices, and more particularly, to power control techniques for radio-frequency circuitry in electronic devices.
Electronic devices such as handheld electronic devices and other portable electronic devices are becoming increasingly popular. Examples of handheld devices include handheld computers, cellular telephones, media players, and hybrid devices that include the functionality of multiple devices of this type. Popular portable electronic devices that are somewhat larger than traditional handheld electronic devices include laptop computers and tablet computers.
Due in part to their mobile nature, portable electronic devices are often provided with wireless communications capabilities. For example, handheld electronic devices may use long-range wireless communications to communicate with wireless base stations. Cellular telephones and other devices with cellular capabilities may communicate using cellular telephone bands at 850 MHz, 900 MHz, 1800 MHz, and 1900 MHz. Portable electronic devices may also use short-range wireless communications links. For example, portable electronic devices may communicate using the Wi-Fi® (IEEE 802.11) bands at 2.4 GHz and 5.0 GHz and the Bluetooth® band at 2.4 GHz. Data communications are also possible at 2100 MHz.
To satisfy consumer demand for small form factor wireless devices, manufacturers are continually striving to reduce the size of components that are used in these devices while providing enhanced functionality. It is generally impractical to completely shield a user of a compact handheld device from transmitted radio-frequency signals. For example, conventional cellular telephone handsets generally emit signals in the vicinity of a user's head during telephone calls. Government regulations limit radio-frequency signal powers. In particular, so-called specific absorption rate (SAR) standards are in place that impose maximum energy absorption limits on handset manufacturers. At the same time, wireless carriers require that the handsets that are used in their networks be capable of producing certain minimum radio-frequency powers so as to ensure satisfactory operation of the handsets.
The manufacturers of electronic devices such as wireless handheld devices therefore face challenges in producing devices with adequate radio-frequency signal strengths that are compliant with applicable government regulations.
It would therefore be desirable to be able to provide electronic devices with improved wireless capabilities.